The National Firearms Act of 1934 defines a “machinegun” as “any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger.” 26 U. S. C. §5845(b). With a machinegun, a shooter can fire multiple times, or even continuously, by engaging the trigger only once. This capability distinguishes a machinegun from a semiautomatic firearm. With a semiautomatic firearm, the shooter can fire only one time by engaging the trigger. Using a technique called bump firing, shooters can fire semiautomatic firearms at rates approaching those of some machineguns. A shooter who bump fires a rifle uses the firearm’s recoil to help rapidly manipulate the trigger. Although bump firing does not require any additional equipment, a “bump stock” is an accessory designed to make the technique easier. A bump stock does not alter the basic mechanics of bump firing, and the trigger still must be released and reengaged to fire each additional shot. For many years, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) consistently took the position that semiautomatic rifles equipped with bump stocks were not machineguns under §5845(b). ATF abruptly changed course when a gunman using semiautomatic rifles equipped with bump stocks fired hundreds of rounds into a crowd in Las Vegas, Nevada, killing 58 people and wounding over 500 more. ATF subsequently proposed a rule that would repudiate its previous guidance and amend its regulations to “clarify” that bump stocks are machineguns. 83 Fed. Reg. 13442. ATF’s Rule ordered owners of bump stocks either to destroy or surrender them to ATF to avoid criminal prosecution. Michael Cargill surrendered two bump stocks to ATF under protest . . .Held: ATF exceeded its statutory authority by issuing a Rule that classifies a bump stock as a “machinegun” under §5845(b).  THOMAS, J., delivered the opinion of the Court, in which ROBERTS, C. J., and ALITO, GORSUCH, KAVANAUGH, and BARRETT, JJ., joined. ALITO, J., filed a concurring opinion. SOTOMAYOR, J., filed a dissenting opinion, in which KAGAN and JACKSON, JJ., joined. Read by RJ Dieken.